Convertible and portable vacuum-blower apparatus are known in the prior art. Such apparatus typically include a housing which holds a motor and an impeller driven by the motor. The impeller communicates with an air inlet and an air outlet. During use as an air blower, an apertured cover is placed over the air inlet and a blower nozzle is attached to the air outlet to direct a stream of air in a desired direction. During use as a vacuum, the apparatus is converted by removing the apertured cover and placing a vacuum nozzle in communication with the air inlet, and substituting a debris bag for the blower nozzle at the air outlet. U.S. Pat. No. 4,325,163 issued on Apr. 20, 1982 to Mattson et al is one such prior art apparatus.
A potential safety hazard in such apparatus exists when the apparatus is being coverted from its blower mode to its vacuum mode, and vice versa. During conversion, the vacuum nozzle or apertured cover are removed from the air inlet, thus exposing the impeller blades. If the motor were accidently turned on while the impeller blades were exposed, a person could be injured by the rotating impeller blades.
Another disadvantage of the prior art convertible blowervacuum apparatus is that they supply the same velocity of air to the air outlet in both the blower and vacuum modes. However, it is desirable to have a higher velocity of air when the apparatus is operating in its blower mode.